Bibliographic details of the publications referred to by author in this specification are collected at the end of the description.
There is an increasing belief that co-delivery of antigen and adjuvant to the same antigen-presenting-cell (APC) is preferable and sometimes essential for induction of appropriate immune responses. For example, the ability of saponin-based adjuvants to induce CD8+ CTL responses is attributed to their ability to cause endosomal escape of antigen, a mechanism which requires co-delivery. Particle formation which comprises a stable complex of adjuvant and antigen is the simplest way to achieve co-delivery. The usefulness of ISCOM™ technology derives partly from the immunomodulatory activity of saponins and partly from their ability to form complexes with hydrophobic or amphipathic immunogens. However, many molecules lack hydrophobic regions and in fact such molecules are preferred as recombinant proteins because of their easier expression and purification.
Accordingly, there is a need to develop immunogenic complexes which facilitate the co-delivery of antigens and carriers which otherwise do not usually form sufficiently stable complexes. For example, complexes comprising antigens which lack hydrophobic regions together with adjuvant.
In work leading up to the present invention, the inventors have developed an immunogenic complex based on the electrostatic association of an antigen and an organic carrier, such as an adjuvant. This electrostatic association permits co-delivery of the antigen and the organic carrier to the immune system. Accordingly, by establishing an electrostatic association, antigens of interest (irrespective of their hydrophobicity) can be co-delivered with an organic carrier, for the purpose, for example, of inducing a cytotoxic T-lymphocyte response to the antigen.